Single-particle Spectroscopic Study On Au@MoS₂ Core-shell Nanostructures

Two-dimensional transition metal sulfides(TMDs)have relatively large exciton binding energy and transition dipole moment.A and B excitons produced by the spin orbit coupling splitting of TMDs at the K point of Brillouin region can interact with the plasmonic resonance of noble metal nanoparticles,leading to the change of the relaxation time of plasmons and excitons.The mechanism can be utilized to modify the optical properties of the composite materials.In this thesis,we prepared gold@molybdenum disulfide(Au@MoS2)core-shell nanostructures by depositing molybdenum disulfide(MoS2)on the surface of gold nanospheres(AuNS)by chemical vapor deposition.The optical properties of the Au@MoS2 core-shell nanostructures were systematically studied mainly by singleparticle dark-field scattering spectroscopy.The specific research contents are as follows:(1)We prepared Au@MoS2 core-shell nanostructures of different sizes on quartz substrates,and characterized the morphology and optical property of Au@MoS2 core-shell nanostructures in situ by scanning electron microscopy and single-particle dark-field scattering imaging and spectroscopy system.We found that due to the influence of A and B excitons in the MoS2 shell,the scattering spectrum of core-shell nanostructure splits and the linewidth of the scattering peak is narrowed.Finally,the scattering spectra of Au@MoS2 core-shell nanostructures obtained by QSA theory and Comsol software verify the experimental results.(2)Compared to the bare AuNS particles,the Au@MoS2 core-shell nanostructures have narrower plasmon resonance linewidths.Therefore,the core-shell structure is supposed to have better plasmonic sensing performance.In this part,we measured its scattering spectra of Au@MoS2 core-shell nanostructures respectively in air and water.The results show that the resonance wavelength of the A and B excitons do not change with the variation of the external refractive index,while the plasmon resonance performs red shifts with the increase of the external refractive index.The calculated sensitivity of the Au@MoS2 core-shell nanostructure is about 266 nm/RIU(RIU=refractive index unit).It shows that the core-shell structure has a good sensing performance.Our study demonstrates that the Au@MoS2 core-shell nanostructures can be applied in nano-optical sensing devices with highly tunable spectral line patterns.